MEMS mass-spring-damper systems using an out-of-plane suspension scheme

Abstract

MEMS mass-spring-damper systems (including MEMS gyroscopes and accelerometers) using an out-of-plane (or vertical) suspension scheme, wherein the suspensions are normal to the proof mass, are disclosed. Such out-of-plane suspension scheme helps such MEMS mass-spring-damper systems achieve inertial grade performance. Methods of fabricating out-of-plane suspensions in MEMS mass-spring-damper systems (including MEMS gyroscopes and accelerometers) are also disclosed.

The invention claimed is: 
     
       1. A MEMS accelerometer, comprising:
 a proof mass; 
 plural anchors distributed in a plane; and 
 a plurality of suspensions, the suspensions connecting between the proof mass and the plural anchors; 
 wherein a longest length of said plurality of suspensions extends out from said plane defined by said plural anchors, and 
 wherein said proof mass is located at least partially directly on top of said plural anchors. 
 
     
     
       2. The MEMS accelerometer of  claim 1 , wherein said MEMS accelerometer is an inertial grade MEMS accelerometer. 
     
     
       3. The MEMS accelerometer of  claim 1 , wherein said proof mass has a length and width ranging from 100 μm to 3 mm and a thickness ranging from 10 μm to 300 μm. 
     
     
       4. The MEMS accelerometer of  claim 1 , wherein said proof mass is comprised of an upper mass and a lower mass. 
     
     
       5. The MEMS accelerometer of  claim 4 , wherein said lower mass has a smaller length than said upper mass. 
     
     
       6. The MEMS accelerometer of  claim 5 , wherein said lower mass is 100 μm to 200 μm shorter in length than said upper mass. 
     
     
       7. The MEMS accelerometer of  claim 4 , wherein each of the plurality of suspensions attached to the plural anchors are also attached to one of the lower and upper masses. 
     
     
       8. The MEMS accelerometer of  claim 1 , wherein said proof mass has a mass ranging from 30 μg to 3 mg. 
     
     
       9. The MEMS accelerometer of  claim 1 , wherein said proof mass, said plural anchors, and said suspensions are comprised of crystalline Silicon. 
     
     
       10. The MEMS accelerometer of  claim 1 , wherein said proof mass rests on said suspensions. 
     
     
       11. The MEMS accelerometer of  claim 1 , wherein said suspensions have a cross-section ranging from 5×5 μm 2  to 100×100 μm 2 . 
     
     
       12. The MEMS accelerometer of  claim 1 , wherein said suspensions have a length ranging from 250 μm to 600 μm. 
     
     
       13. The MEMS accelerometer of  claim 1 , wherein said MEMS accelerometer is bulk micromachined. 
     
     
       14. The MEMS accelerometer of  claim 1 , wherein the proof mass extends in another plane, different than, but parallel to the plane in which the plural anchors are distributed. 
     
     
       15. The MEMS accelerometer of  claim 1 , wherein each of the plurality of suspensions attached to the plural anchors are also attached to a single part of the proof mass.